1. Field of the Invention
The invention is concerned with an arrangement for the operation of multiple radio controlled terminal devices using a common antenna.
2. Description of the Related Art
In general, the number of terminal devices for mobile communications is increasing in vehicles such as, for example, busses, automobiles, etc. Therein, besides employment for audio transmissions, these terminal devices (also referred to as mobile telephone devices) are employed ever frequently for the transmission of data in telephonic or emergency assistance systems.
Both for optical reasons as well as for space and cost considerations the number of antennae on the vehicle required for this increasing number of terminal devices cannot be increased without limit.
From DE-A-195 47 288 A1 the radio station with a setoff or separate antenna unit is known, wherein a duplexer is provided close to the antenna. Beyond this, a pre-amplifier is likewise provided close to the antenna. This antenna unit is in the form of a unit integrated with the transmitter and receiver antenna and is in communication via two dedicated separated transmission and receiving branches with unidirectional transmitter or receiver units.
From U.S. Pat. No. 4,228,544 a transmitter and receiver unit for vehicles is known with a common transmitter and receiver antenna, wherein the base of the transmitter and receiver antenna is connected with an aerial combining unit in the immediate vicinity of the transmitter and receiver antenna. A preamplifier connected with the aerial combining unit is likewise provided in the immediate vicinity of the antenna base.